Process of controlling the thickness of walls in an electric furnace



C. H. CHAPMAN.

PROCESS 0F CUNTRULLING THE HlcKNEss of WALLS IN AN ELECTRIC rURNAcE.

WPLICATION HLEU FEB. 20. |911.

1,340, 1 55.` Patented May 18, 1920.

\| IKN Willmann l f// 3M fig' www ummm Noms,

, UNITED sTATEs PATENT oEEIoE.

cHAELEsH. CHAPMAN or NIAGARA EALts, NEW Yom; AssmNoB, 'ro GENERAL ABRASIVE COMPANY, INC., or NIAGARA FALLS, NEW Yom, A CORPORATION or, NEW roux.

,'PEocEss or etnici:harinasY THE THICKNEss oF WALLS IN AN ELECTRIC FUENACE.

the furnace ining of refractory material by. fusing the. charge and subsequently controlling the thickness of this liningr either by regulating the rate of feeding .the charge relative to the amount of meltinglr heat applied or byregulating the heat relative to the rate of feeding the charge.

Many types of furnace walls have been used in high temperature electric furnaces. Among these may be mentioned ca rbon lined i walls of firehrick; rnagnesia brick; chrome brick; silica. -brick; water jacketed brick walls; water jackted metal walls; water sprayed metal .wallsgand various combinations of these arrangements. All of these are subject to more or less rapid deteriorw tion in operation.y temperatures attained andthe varying conditions inthe furnace, which are sometimes highly reducing" and sometimes oxidizing, combine to rapidly destroy the furnace walls, and not infrequently meltl through theni so that the molten charge escapes at no little danger to the operators, and expense by the loss of-much material. "The cost of re-lining and repairing electric furnace walls has heretofore constituted a serious item of expense in electric srneltingr processes. The method of constructing and operati ng clertric furnaces which I have invented obviates all necessity for re-lining or mpairing the furnace walls as it causes them to he anto- ..matically renewed so that a furnace will last indefinitely. ,4

`My inventionrelates more particularly to tapping or tilting f" aces of the continuous type, but l do not rc. =rilct my invention to these types as the same may be used in Specification of Letters Patent.

. devices.

The exceedingly high Patented May 1s, 1920.

' 'Application led February 20,1917. Serial No. 149,948.

any other type of furnace to which it may `he adapted.

iVith these and other objects in view, the

invention consist-s of certain'novel features as will be more f ully described, and particularly pointed out in the appended claims.

In the accompanying drawing:

The figure illustrated in the drawing is a, sectional side elevation showingone form of furnace by the use of which my improved process may be successfully carried out.

{eferring to the drawing, 10 designates the bottom and side walls of the electric smeltingir furnace the walls of which may be made of tiebrick or other suitable refractory material, and reinforced on the outside by means of metal bands or other suitable Any desired number of electrodes 11 may be employed to carry the electric current into the .furnace for melting the charge. TheseV nay be supported on wire cables 12 and counter balanced by weights 13 so that Vthey can be raised or lowered Vas needed to regulate the amount' of current passing through the charge. 14,(lesignates that portion of the charge which is in a molten state and 15 that part of the charge which has previously been melted but has flowed away from the molten zone in the immediate vicinity of the electrodes to a position where the temperature is insufficient to keep it molten andI where it has hardened, so forming a solid,unbroken, continuous inner wall or lining of highlyrefractry material like lava, which serves to protect both the sides and the bottom of the brick walls of` the furnace from' action of the exccssive heat and so prolonge the life of the vicinity of the electrodes; cools into a solid crystalline'highly refractory shell, which is much more refractory than the granular charger from which it was formed, thereby providingr a solid unbroken cont inuons highl)1 refractory lining for the furnace that can be obtained onl)r in the manner above described.

In the operation of' an electric smclting furnace it is custonnuv and desirable to keep the amount of current passingr through it nearly constant and this is accomplished by raising or lowering the electrodes to compensate for the varying depth of the charge fed at intervals thereto. The amount of head added to the charge per unit of time is therefore approximately uniform. It therefore followsthat if no additional charge be added for a consii'lerable period of time the melted part of the charge 14 will take up Aall the heat and become continuallyy hotter.

Some. of this heat travels by radiation and conduction from 14 into the outlying strata 15 which may be that previousl)r melted and subseqfently cooled or it may be part ot' an original unmelted charge and the temperature of this molten bod)v ac'ts upon and meltsl the walls with which it contactsl thus en-V larging the molten zone in thc furnace. On the other hand'if new charge be added faster than it can be melted b v the h at available from the current. the temperature ol' charge 1-l will decrease and will fall to a point where it will begin to harden along the surface of contact between 1-1 and l5. thus decreasing the molten zone 14 and thickening the solidified inner wall 15. B v regulating the rate of feeding in thc new charge. the inner wall 14 can thus bc maintained at any desired thickness` In practice I have found that this principle 1s also susceptible of local application in the furnace. the operation of electric smelting furnaces: that the charge, has a tendencyto burn or melt through. the. walls at one spot or another as indicated by the dotted line at 1G. The imminence of this condition is indicated by the glowing red color which appears on the outside of the walls at the point threatened. By feeding into the furnace new charge,"A at this locality the temperature, is lowered, the wall 16 re-forms, and the molten part of the charge 14 is reduced to the proper size. However, this dangerous condition rarely occurs when the correct tem Experience. has shown in perature of the charge 14 is'maintained by suitable regulation of the charge which l accomplish h v the means described above.

I find that in o )erating the furnace in the manner describe( there 1s a gradual expan sion of the outside of the walls 15 so that in time the irebrick 10 may fall away and only the. then thickened wall l5 ranains. As this may be huilt up at willon the inside, either as a whole or locally, the life of the furnace is unlimited in duration, and no expense is required for new linings or other re `uurs.

have described the method of maintaining the desired thickness of furnace walls by maintaining a constant melting heat and varvmg or regulating thl rate, of feeding the charge which is the preferred mode of operation; but in some cases it may be (lesired to provide a constant rate of feeding the charge aml to var v the intensity of the melting current. which arrangement also falls within the spirit of my invention. I desire it to be understood that although specific terms are employed they are used in a generic and descriptive scuse and not for the purpose of limitation. the scope of the invention being defined by 4the appended claims.

I claim:

1. An improved method of constructing' furnace walls, which consists' in first melting and then cooling a portion of the charge whereby the cooled portion forms a solid continuoushomogeneous crystalline heat-re sisting wall about the center portion which 'provides a receptacle for the molten mass.

Q. An improved method et constructing:Ir furnace walls. which consists in first melting and then cooling a portion of the charge whereby the cooled portion forms a solid continuous homogeneous crystalline 'lientresisting wall about the center portion which provides a receptacle for the molten mass, said walls heilig maintained of the desired working thickness by controlling the rate of feeding the charge relative to the amount of heat applied.

In testimony wlizereof I atlix in presence o two witnesses.

CHARLES H. CHAPMAN. llitncsses lxoYAL D.' '.loalLlNsoN, CnAuLEs Loouwoon.

my signature 

